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Posted By Topic: law on junctions and joins

craigG
Aug 07 2013 20:05

Hi all. Just reading through 3000. Looking for info on joining of cables , within walls etc. Now i have been advised it is ok to have basic insulation inside a wall. But reading 3.10.1.1 i think it was the only time this js acceptable is within 100 mm of say a swich or powepoint. Other than that it if its basic ins then it must be either reinstated to the orgina ( ie crimp sleaves and heat shrink ) or say a j.box over it. Pretty easy. But what about joints?? If you say join 3 cables together inside a wall , and remove the sheathing to do this , it reads it must be in a box. Does the junction box legally have to be accessable? I always thorght it did , but i cant seam to find it now. Also if ya solder the cores , then usr heatshrink over the solderd tabs , what would be wrong with a jbox over that , inside a wal cavaty? , id prefur to do that than have conntectors in the box behind the wall. Also it says that eath connections shall not rely on the solder alone , meaning some other type of conection over thr earth is needed too , but it also says that soldered connections must not be under a clamp , so how do you athieve this if you solder an earth?.....cant rely on solder alone , but also cant put it under a clamp! Buggerd. Purhaps i am missing something here. Appreciate ya inputs , cheers. Craig.
   

Hedley
Aug 07 2013 21:15

Just because you can\'t find a rule prohibiting it in the rule book doesn\'t make it acceptable as a general practice.
As a general rule all joints that are not made with crimp connectors and insulated to the original standard should be available for inspection. Something that is hard to do if it is sealed in a wall cavity.
Joining 3 cables in a wall is even worse and using screwed type connectors in a joint in the wall would be completely unacceptable from a good trade practice point of view.
Soldered joints in installation wiring are for Australians. Use screwed connectors in accessible junction boxes like the professionals if you have to join cables.
   

craigG
Aug 07 2013 21:25

I know what is good practice and what is not. I wad asking legally. I mean if u have to join cables in a wall , the best way is to crimp sleave and heat shrink i know. But when the time comes u run out of crimls kr whatever , what is another way of doing it legally ? I just want to know if soldering behind a wall , and fitting a j.b is agaist thr rules , aleck? I myself no not do it , but my new work mate does , ive tryed to tell him its not good , but was debating the legal side of it.?
   

pluto
Aug 08 2013 07:59

When AS/NZS 3000:2000 was being drafted in the late 1990s the use of soldering as a method of terminating and joining of conductors in Australia was reduced, and in particular, when a terminal screw was also being used the practice was deemed to be unsatisfactory. This was due to the fact that a solder lug when under high fault current conditions the solder joint heats up and the connection usually fails and goes open circuit. If the connection is a protective earth connection this could be hazardous.

If you look at the current AS/NZS 3000 + A1 + A2 in clause 3.3.2.8 (c) and section 3.7 there are a number of additional requirements that make the use of solder as the sole method of ensuring electrical conductivity of the joined conductor as being not good practice under a wide range of conditions.
   

AlecK
Aug 08 2013 14:53

3.7.2.11 says a connection in an earthing conductor is no allowed to be by solder alone
   

craigG
Aug 08 2013 20:59

Ok i have an instance where i have 3 2.5s in a wall i want to exteened to reach to a new location , i cant pull wires up cos they go accross the wall. The nrw powerpoint is only 1/2 a meter from the cables , u saying the only acceptable way would be to join each wire and have 3 new tails at the new plug ? 9 crimps. How else could you actually do it? Craig.
   

Daniel
Aug 08 2013 21:10

Well common sense really. If you have roof access you could pull the three cables back to a junction box and take one 2.5 mm2 down to the socket outlet.

Alternatively, crimp join the three. It actually doesn\'t take that long: about 5 - 10 mins.
   

Daniel
Aug 08 2013 21:12

* Crimp join each cable separately (3 individual cables).
   

Rob
Aug 09 2013 07:20

When you explain that accessible joins means protection against fire and simplified maintenance/upgrades some customers are quite happy with a flush box and blanking plate.
   

dont
Aug 09 2013 07:33

see how its protecting against fire... servicable and all that sure, but thats it really... if its a bad join its a bad join whether its accessible without removing the wall lining or not
seen more fire risk from vermin damage than bad joins to be honest
though of course best practice is to make things accessible
someone might care to mention that to plumbers when situating hot water cylinders perhaps
;o)
   

So
Aug 09 2013 12:05

The argument seems to be that crimp and sleeve is best, screw terminals with j-box on the wall is also good provided the customer doesn\'t mind, screw terminals in a flush box (i.e. in the wall) under a blanking plate is also good if the customer is happy.

Soldering earth is unacceptable if there is no additional restraint, but metal clamping is not allowed with soldering so not sure how you provide an extra restraint such that the soldering is still worth doing.

Meanwhile screw terminals in a j-box behind a wall is legal but bad practice, j-box behind a blanking plate slightly better, and a blanking plate with no flush box or j-box appears to be legal but terrible practice (assuming a wall counts as an enclosure), and likewise screw terminals fully enclosed in the wall. If the wall doesn\'t qualify (does it?) then you\'d have to sheath your terminals to reinstate the insulation, but that\'s all you\'d need to be legal (but not good).

Fair summary?
   

craigG
Aug 09 2013 20:19

Thank you, thats what i wanted to know. Is it legal , would it be an offene to have a jbox conceled in a wall and could thr ewrb disapline u for it. We all no its noy goood , and i would neaver do it , like to hear alek k opinion on this
   

Rob
Aug 10 2013 09:59

don\'t,

High impedance joins heat up. Walls contain combustible materials. Heat + combustible materials may cause fire.

Have you never seen a burnt out MCB where the cable in was loose or missed the screw terminal during installation.

To quote Rachel, \"It may not happen overnight, but it will happen.\"
   

sorry but i still
Aug 10 2013 10:38

dont see how making the join accesible is PROTECTING against fire Rob... all its doing is making the join accessible

the QUALIITY of the join is what could potentially create a fire risk

whether or not the join is accessible or not doesnt make a bad join any safer as far as i can see and similarly i cant see how being accessible makes a good join any less safe

;o)
   

BC
Aug 10 2013 12:28

You could try 3.7.2.3.1 page 131. My take has always been junction boxes in walls can loosen up over time. Don\'t fancy having to tell the customer they have to rip open their walls to locate a fault. A flush box and blank plate join on the other hand does give the option of being able to split circuits out. Others may have but I\'ve not (yet) seen a crimp failure in a wall. Would be nice if the powers that be had seen fit to include in 3.7.2.9.2 Prohibited joints-THOU MUST NOT PUT J/BOXES IN WALL CAVITIES.....
   

BC
Aug 10 2013 12:30

Sorry that was aerial cables but you get the idea...
   

Daniel
Aug 10 2013 21:54

I can\'t believe how its NOT against the regs to be installing junction boxes behind wall cavities that are inaccessible.

WTF.


   

Rob
Aug 11 2013 10:55

When a joint is accessible there is the opportunity for that joint to be maintained. With proper maintenance the risk of fire through joint failure is reduced.

While working in a switchboard you naturally check security of all accessible connections. Most often you get a quarter turn out of each screw. Not because the installer was slack, but because the copper has extruded under pressure from the screw terminal.

Same applies when working on sub circuits. If you come across a join you can give it a tweak. If the join is hidden in a wall then you can\'t.

My conclusion accessible joins carry lower risk than inaccessible joins.

Rules and regs are the minimum acceptable standard. I try to aim higher than that.
   

AlecK
Aug 11 2013 11:17

Also worth looking at ESR20 (2)(i): it\'s electrically unsafe if you can\'t access the joint as required. So a screw terminal requires access for maintenance but a crimp connection , properly done and insulated, is permanent and no maintenance can be carried out so access is not required.

Still thinking about whether an outer glue-lined heavy-all heatshrink such as WCSM would be OK as strain relief to allow solder joint of PEC, but am thinking it probably is.
   

Rob
Aug 11 2013 11:42

AlecK, just curious. Where is it stated what constitutes a \"properly done\" crimp joint? Is there a minimum strain it must withstand and maximum allowed impedance?

Large CSA crimps come with manufacturer\'s instructions directing die size and the like. But what about the smaller crimps that might be used in a small CSA TPS joint? One size typically covers a range of CSA and hand tools apply variable pressure.
   

pluto
Aug 11 2013 17:38

When crimping was allowed in as/nzs3000 you will note that it has a few more words added at the end which everyone seems to forget \"and techniques specified by the manufacturer.\" Clause 3.7.2.3.2,

This means the correct lug for the cable and crimped with the correct tool and with the correct indentation. If these 3 conditions don\'t happen the crimp joint may be considered to be unsafe.
   

Rob
Aug 11 2013 20:26

3.7.2.3.2 is ambiguous. Which manufacturer? Cable, crimp or tool?
   

pluto
Aug 11 2013 20:48

The most important is the crimp lug, all the others are needed to match the crimp lug.
   

So
Aug 12 2013 14:36

to get back to the original question, AlecK\'s comment re ESR20 suggests jbox in a wall is not legal unless you have a blanking plate or something to give access to it. Likewise screw terminals (or solder + glue heatshrink?) in a wall with no access. Still nothing definitive on screw terminals or solder behind a blanking plate with no flush box. Both look dumb but legal to me...
   

Rick77
Aug 13 2019 20:22

So if it is legal to leave crimps in wall, how do you crimp 3 cables together. I mean 3 lives 3 neutrals and 3 earths. Is it legal to put more than one core in a crimp terminal.
   

pluto
Aug 14 2019 07:14

Only if the crimp lug was designed for 3 cable cores and fitted incordance with the manufactures instructions.

There few cable lugs that are designed for multiple cable cores.

Refer to AS/NZS 3000 clause 3.7.2.3.2